| 摘要 |
An electromagnetic device comprises an inner member having a pair of helical ribs on its peripheral surface, and windings whereby the ribs can be polarized so that the ribs assume opposite magnetic polarity. An outer member formed from magnetic material surrounds the inner member in spaced relationship and a further member is located in the annular space between the inner and outer members. The inner member comprises a pair of helical elements which when current flows through the windings are attracted to the ribs. The helical elements each have the characteristic of a spring and can deform to provide a progressive increase in the force available at one end of the further member. |
